Estrogen and progesterone effects on transcapillary fluid dynamics

The purpose of this study was to determine estrogen (E2) and progesterone (P4) effects on atrial natriuretic peptide (ANP) control of plasma volume (PV) and transcapillary fluid dynamics. To this end, we suppressed reproductive function in 12 women (age 21–35 yr) using a gonadotropin releasing-hormone (GnRH) analog (leuprolide acetate) for 5 wk. During the 5th week, the women either received 4 days of E2administration (17β-estradiol, transdermal patch, 0.1 mg/day) or 4 days of E2 with P4 administration (vaginal gel, 90 mg P4 twice per day). At the end of the 4th and 5th week of GnRH analog and hormone administration, we determined PV (Evans blue dye) and changes in PV and forearm capillary filtration coefficient (CFC) during a 120-min infusion of ANP (5 ng · kg body wt−1 · min−1). Preinfusion PV was estimated from Evans blue dye measurement taken over the last 30 min of infusion based on changes in hematocrit. E2 treatment did not affect preinfusion PV relative to GnRH analog alone (45.3 ± 3.1 vs. 45.4 ± 3.1 ml/kg). During ANP infusion CFC was greater during E2 treatment compared with GnRH analog alone (6.5 ± 1.4 vs. 4.9 ± 1.4 μl · 100 g−1 · min−1 mmHg−1, P < 0.05). The %PV loss during ANP infusion was similar for E2 and GnRH analog-alone treatments (−0.8 ± 0.2 and −1.0 ± 0.2 ml/kg, respectively), indicating the change in CFC had little systemic effect on ANP-related changes in PV. Estimated baseline PV was reduced by E2-P4treatment. During ANP infusion CFC was ∼30% lower during E2-P4 (6.0 ± 0.5 vs. 4.3 ± 4.3 μl · 100 g−1 · min−1mmHg−1, P < 0.05), and the PV loss during ANP infusion was attenuated (−0.9 ± 0.2 and −0.2 ± 0.2 ml/kg for GnRH analog-alone and E2-P4treatments, respectively). Thus the E2-P4treatment lowered CFC and reduced PV loss during ANP infusion.